1. Field of the Invention
The disclosure generally relates to oilfield applications having multiple fluid lines for servicing wells. More particularly, the disclosure relates to oilfield applications having manifolds that carry slurries with liquids and particles.
2. Description of the Related Art
FIG. 1A is an exemplary schematic diagram of a prior art fracturing system for an oilfield fracturing operation. FIG. 1B is an exemplary schematic diagram of a prior art fracturing system, showing fractures in an underlying formation. FIG. 1C is an exemplary schematic diagram of the prior art fracturing system of FIG. 1A detailing a system for one well. The figures will be described in conjunction with each other. Oilfield applications often require pumping fluids into or out of drilled well bores 22 in geological formations 24. For example, hydraulic fracturing (also known as “fracing”) is a process that results in the creation of fractures 26 in rocks, the goal of which is to increase the output of a well 12. Hydraulic fracturing enables the production of natural gas and oil from rock formations deep below the earth's surface (generally 5,000-20,000 feet). At such depths, there may not be sufficient porosity and permeability to allow natural gas and oil to flow from the rock into the wellbore 22 at economic rates. The fracture 26 provides a conductive path connecting a larger area of the reservoir to the well, thereby increasing the area from which natural gas and liquids can be recovered from the targeted formation. The hydraulic fracture 26 is formed by pumping a fracturing fluid into the wellbore 22 at a rate sufficient to increase the pressure downhole to a value in excess of the fracture gradient of the formation rock. The fracture fluid can be any number of fluids, ranging from water to gels, foams, nitrogen, carbon dioxide, or air in some cases. The pressure causes the formation to crack, allowing the fracturing fluid to enter and extend the crack further into the formation.
To keep the fractures open after the injection stops, propping agents are introduced into the fracturing fluid and pumped into the fractures to extend the breaks and pack them with proppants, or small spheres generally composed of quartz sand grains, ceramic spheres, or aluminum oxide pellets. The proppant is chosen to be higher in permeability than the surrounding formation, and the propped hydraulic fracture then becomes a high permeability conduit through which the formation fluids can flow to the well.
In general, hydraulic fracturing equipment used in oil and natural gas fields usually includes frac tanks with fracturing fluid coupled through hoses to a slurry blender, one or more high-pressure, high volume fracturing pumps to pump the fracturing fluid to the well, and a monitoring unit. Associated equipment includes fracturing tanks, high-pressure treating iron, a chemical additive unit (used to monitor accurately chemical addition), pipes, and gauges for flow rates, fluid density, and treating pressure. Fracturing equipment operates over a range of pressures and injection rates, and can reach up to 15,000 psi (100 MPa) and 100 barrels per minute (265 L/s). Many frac pumps are typically used at any given time to maintain the very high, required flow rates into the well.
In the exemplary prior art fracturing system 2, fracturing tanks 4A-4F (generally “4”) deliver fracturing fluids to the well site and specifically to one or more blenders 8. The tanks 4 each supply the fluids typically through hoses 6A-6F (generally “6”) or other conduit to one or more blenders 8. One or more proppant storage units 3 can be fluidicly coupled to the blenders 8 to provide sand or other proppant to the blenders. Other chemicals can be delivered to the blenders for mixing. In most applications, the blenders 8 mix the fracturing fluids and proppant, and delivers the mixed fluid to one or more trucks 5A-5E (generally “5”) having high-pressure pumps 9A-9F (generally “9”) to provide the fluid through one or more supply lines 10A-10E (generally “10”) to a well 12A (generally “12”). The fluid is flushed out of a well using a line 14 that is connected to a dump tank 16. The fracturing operations are completed on the well 12A, and can be moved to other wells 12B and 12C, if desired.
One of the significant challenges in fracturing operations is the large number of trucks, pumps, containers, hoses or other conduits, and other equipment for a fracturing system. While FIG. 1B is a graphic artist's schematic helpful for understanding larger components of a fracturing system, and FIG. 1C is helpful for schematically linking the components, the systems of FIGS. 1B and 1C are vastly simplified. The reality of a well site is shown in FIGS. 2A and 2B. The complexity and the equipment, piping, and hoses required just for one well is significant and expensive. Further, the equipment and connections are disassembled, relocated, and reassembled for the next well, further adding to increased costs for performing fracturing jobs on a field having multiple wells. The difficulty of working around the wells with the large number of components also causes safety issues.
FIG. 2A is a pictorial representation of a well site facing toward a single well, showing the equipment for fracturing the well including a conglomeration of multiple blenders, pumps, piping, hoses, and other lines. FIG. 2B is a pictorial representation of the well site shown in FIG. 2A taken from the well facing outward to the equipment. The figures will be described in conjunction with each other. The blenders 8 provide the mixed fluids through several blender lines 11 to a trailer 20 having a low-pressure input line 21 that aggregates the fluid from the blender lines. The low-pressure input line 21 flows the fluid into a low pressure outline 23 from which several pump input lines 25 coupled thereto receive the fluid and deliver the fluid to the high-pressure pumps 9. The pumps 9 provide high-pressure fluid through a pump output line 27 to a high-pressure input line 28 on the trailer 20. Several supply lines 10, coupled to the high-pressure input line 28, deliver fluid to the well 12 for the fracturing. Some supply lines have further connections to high-pressure pump output lines to increase capacity adding to the complexity of the piping system. For example, as shown in FIG. 2B, a supply line 10A is also coupled directly with a pump output line 27A and supply line 10B is also coupled directly with a pump output line 27B.
Recently, efforts in the industry have been directed to more efficiently fracture multiple wells at a given field. The number of assembled equipment components has raised even further the complexity level of the system and the ability to operate in and around the multiple wells. One need for an improved system is to provide a better transfer of the fluid from the many sources to the well.
Copending application Ser. No. 13/006,272 describes a solution of an adjustable modular skid system having one or more manifolds for aggregating the typical hoses and other conduits in a typical oil field services system. Flushing and otherwise draining the manifolds can be necessary, for example, when disassembling the manifolds for use at other locations or for other operations, or when flushing the manifolds with clean water. It is preferred to drain the manifolds through the last portion of the manifolds, that is, the ends of the manifolds. However, the manifolds may fill and become restricted or plugged on one or more ends of the manifolds and other non-flowing portions of the manifolds. Draining the manifolds can become problematic with restricted or plugged lines. Further, pressure spikes in the plugged portions can lead to pipe burst. Even if other portions of the system are drained prior to disassembly, any remaining pressure between the portion to be disassembled and the plugged section can cause an unsafe pressure release at disassembly.
There remains a need for an improved system to enhance the ability to flow fluid through the manifolds and drain the manifolds, and particularly drain the ends of the manifolds.